Has MLB bullpen usage reached a state of stagnation?

From Zack Meisel at MLB.com on May 14, 2012, with mention of SABR members Gary Gillette and Paul Hirsch:

Nearly one-third of Major League clubs have changed closers this season because of subpar performances. Another handful of teams lost their finishers to injuries. Yet, as elusive as bullpen consistency has been, teams have maintained their standard methods of employing their relievers. As much as the game has evolved, bullpen usage appears to have reached a state of stagnation.

"It's just easier to go along with the idea of 'Well, that's the way it is,'" said Indians closer Chris Perez.

But is the established method of using relievers simply a case of groupthink?

Over time, starting pitchers have been conditioned to throw once every five days, instead of four, and for only 100 or so pitches. That has placed pressure on teams to fortify their staffs with a slew of reliable relievers. Starters have thrown complete games in just two percent of their outings this season, compared to 44 percent in 1940 and 82 percent in 1900.

"You definitely need a good bullpen," said Indians southpaw Tony Sipp. "It takes a lot of pressure off the starters if they know that if they can just get to the sixth, then you have a good bullpen coming behind you. It can definitely make or break a team."